Dibromine trioxide is the chemical compound composed of bromine and oxygen with the formula Br2O3.

It has the structure Br−O−BrO2 (bromine bromate).

The Br−OBrO2 bond length is 1.845 Å, the O−BrO2 bond length is 1.855 Å and the Br=O bond length is 1.612 Å.

[4] Dibromine trioxide can be prepared by reacting a solution of bromine in dichloromethane with ozone at low temperatures.

[3][5] It disproportionates in alkali solutions to Br− and BrO−3.